Bulk viscous fluid in extended symmetric teleparallel gravity

TL;DR

This paper explores bulk viscous cosmological models within extended symmetric teleparallel gravity, deriving solutions that describe the universe's transition from deceleration to acceleration, and aligns well with recent observations.

Contribution

It introduces exact solutions for bulk viscous FLRW models in $f(Q,T)$ gravity with specific matter-non-metricity couplings, highlighting the universe's dynamic acceleration phases.

Findings

Models exhibit a transition from deceleration to acceleration.

Cosmological parameters align with recent astronomical data.

Viscous effects influence the universe's expansion dynamics.

Abstract

In this paper, we investigate the existence of bulk viscous FLRW cosmological models in a recently proposed extended symmetric teleparallel gravity or $f\left( Q,T\right) $ gravity in which $Q$ is the non-metricity and $T$ is the trace of the energy-momentum tensor. We consider a simple coupling between matter and non-metricity, specifically, $f\left( Q,T\right) =\alpha Q^{m+1}+\lambda T$ and $f\left( Q,T\right) =\alpha Q+\lambda T$ where $\alpha $, $\lambda $ and $m$ are free model parameters. The exact cosmological solutions are found by assuming the scale factor in the form of the hybrid expansion law. This type of relation generates a time-varying deceleration parameter with the transition of the Universe from the early decelerating phase to the present accelerating phase. In the presence of viscous fluid, we analyze some cosmological parameters of our cosmological model such as the energy density, bulk viscous pressure, bulk viscous coefficient, equation of state parameter, and energy conditions. Finally, we conclude our $f\left( Q,T\right) $\ cosmological models agree with the recent astronomical observations.